The long-term goal of the proposed research is to understand the mechanisms by which oxidative stress causes senescence-associated losses in cellular functions. Hypothesis: The specific hypothesis to be tested is that "accrual of oxidative damage to specific proteins is responsible for the senescence-associated losses in cellular functions." The main idea to be scrutinized is that oxidative damage to specific proteins determines both the nature and the rate of progression of deleterious functional alterations occurring during the aging process. Specific aims: Studies will be conducted on mitochondrial and cytosolic proteins in the flight muscles of Drosophila melanogaster, as the flying ability of the flies gradually declines during aging. Specific proteins exhibiting an age-related increase in oxidative damage, indicated by carbonylation, and loss in catalytic activity will be identified. Causal association between oxidative damage to protein targets and the aging process will be tested in transgenic and mutant flies, which, respectively, overexpress and underexpress the genes encoding the proteins susceptible to oxidative damage. In addition, comparison of oxidative damage will be made between transgenic or genetically selected long-lived and control flies. Significance: Results of this study should provide important new knowledge about: (1) Mechanisms linking oxidative stress to the losses in physiological functions during aging and thus provide a further critical test of the validity of oxidative stress hypothesis of aging. (2) Identify targets of protein oxidative damage during aging and the consequent metabolic failures. Novelty: The idea that protein oxidative damage is a selective and not a random phenomenon is new and challenges the current concepts. The experimental approach will employ new methodology for the quantification of carbonylation of specific proteins as well as unique genetic strategies to test cause-and-effect relationships between the oxidation of specific proteins and the rate of the aging process.